Reduced size electromagnetic device

ABSTRACT

An electromagnetic device of significantly reduced size is provided by the specific designs of the end shields of the device and by the specific designs of insulating end caps of the device that insulate the electrical component parts of the device from contact and possible shorting with mechanical structural parts of the device.

This patent application is a continuation of patent application Ser. No.09/148,652, filed Sep. 4, 1998 and now abandoned.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention pertains to the construction of an electromagneticdevice, such as an electric motor or electric generator, where componentparts of the electromagnetic device have been redesigned tosignificantly reduce its size.

(2) Description of the Related Art

Current trends in the design of electromagnetic machines such as motorshave lead to compact designs of high efficiency motors. The motordesigns have obtained high power to weight and high power to size ratiosthrough their use of high magnetic flux density magnets on their rotorsand high density windings on their stators.

Compact high efficiency motors are constructed of basically the samecomponent parts of larger motors, those being a casing or housing shellcontaining the stator, a pair of end shields attached to opposite endsof the stator, and a rotor supported for rotation in the stator bore bya pair of bearings mounted in the end shields.

In the reduction in size of these high efficiency motors the surfaceareas of motor component parts available for use in establishing secureconnections between the component parts is also reduced. For example, inthe construction of a larger motor there are typically substantial areason interfacing surfaces of motor component parts, such as a stator andan end shield, to accommodate connectors such as nut and bolt connectorsto securely hold the two component parts together. With the ample areasavailable on the interfacing surfaces of the component parts, largerconnectors may be employed to securely hold the component partstogether. However, when the motor is significantly reduced in size, allof its component parts are reduced including the interfacing surfaces ofmating component parts and the connectors employed in securely holdingthe component parts together. In reduced size motors, the componentparts must be redesigned in order to provide the needed secureconnections between the component parts.

A reduction in motor size also requires positioning all of the motorcomponent parts closer together. This includes the electrical componentparts of the motor such as the stator winding, and the structuralcomponent parts of the motor such as the end shields. Reduced motor sizebrings the end shields much closer to the end turns of the statorwinding presenting the undesirable possibility of arcing or shorting ofthe stator winding with the metal end shields. The reduction in sizebringing component parts closer together also presents the problem ofheat generated in one area of the motor adversely affecting another areaof the motor, for example, the electronics of the motor. The componentparts of the reduced size motor must be redesigned to avoid thepotential problems of shorting and heat affecting motor performance.

SUMMARY OF THE INVENTION

The present invention is an electromagnetic device, such as a motor,having component parts that are assembled together to provide a motor ofcompact size having high efficiency. The novel features of the inventionare in the constructions of the component parts and, although describedas applied to a motor, they may also be applied to alternators andgenerators.

The motor of the invention is basically comprised of a stator containingthe stator winding, a pair of end caps attached to axially opposite endsof the stator and insulating the end turns of the stator winding fromthe metal laminations of the stator, an insulator attached over one ofthe end caps, a pair of end shields, one attached over the end cap atone end of the stator and the other attached over the insulator at theopposite end of the stator, and a rotor. The novel features of the motorare primarily in its component parts assembled at the axially oppositeends of the stator. Therefore, the stator construction and rotorconstruction are described in only general terms with it beingunderstood that alternative stator and rotor constructions may beemployed with the invention.

The stator is comprised of a stack of individual stator laminations witheach lamination having a generally octagonal peripheral edge and aplurality of stator poles extending radially inwardly toward a centerbore of the laminate as is typical in many stator constructions.However, the octagonal shape of the peripheral edge is one of the novelfeatures of the motor construction that contributes to the secureconnection of the motor's component parts. With the stator laminatesarranged in a stator stack, the exterior surface of the stator stack isoctagonal and includes four spatially arranged pairs of flat surfacesseparated by a semi-circular trough. The four pairs of flat surfaces andtheir middle troughs extend axially over the exterior surface of thestator stack between longitudinally opposite first and second endsurfaces of the stator stack.

The first and second end caps are assembled over the opposite first andsecond end surfaces of the stator stack. Each end cap is constructed ofan insulating material and includes a plurality of posts radiatinginwardly toward a center bore of the cap. The posts are configuredcomplimentary to the poles of the stator laminations and overlay thestator poles at the axially opposite ends of the stator. The end turnsof the stator winding are wrapped around each of the end cap posts andin this manner the posts insulate the end turns from the metal of thestator poles. In addition, the first end cap at the first end of thestator has a spacer projecting therefrom. The spacer projectslongitudinally and axially outwardly from the first end cap beyond thestator end turns wrapped around the posts of the first end cap. Thespacer engages against the first end shield attached to the stator stackover the first end cap and thereby spaces the metal of the end shieldfrom the turns in the stator winding ensuring that a short will notoccur between the first end shield and the stator winding.

Thus second end cap, like the first end cap, is constructed of aninsulating material and also includes inwardly radiating posts. Endturns in the stator winding at the second end of the stator are wrappedaround the posts of the second end cap in a conventional manner. Inaddition, the second end cap has supports for male terminal connectorsthat are connected to electrical leads of the stator winding. Thesupports project longitudinally and axially outwardly from the secondend cap and securely hold the male electric terminals in a desiredorientation that facilitates the assembly of the motor component parts.

The insulator is attached over the second end cap and the second end ofthe stator stack. The insulator is constructed of an electricallyinsulating and thermally insulating material. Its construction coversover the end turns of the stator winding at the second end of the statorand thereby insulates the end turns from the metal of the second endshield attached to the second end of the stator. In addition, theinsulator thermally insulates any electronic components used inassociation with the motor and attached to the second end shield fromthe heat generated in the stator. The insulator is also formed withtubular lead guides corresponding to each of the male electric terminalssupported by the second end cap. The tubular lead guides projectlongitudinally and axially outwardly from the insulator and surroundeach of the male terminals supported by the second end cap.

The second end shield is constructed with lead openings corresponding tothe number of male terminals supported by the second end cap and thenumber of tubular lead guides on the insulator surrounding theterminals. The lead openings in the second end shield are positioned sothat the tubular lead guides will pass through the openings and in thismanner the tubular lead guides of the insulator also insulate theelectric terminals of the stator from the metal of the second endshield. The tubular lead guides also positively position the maleelectric terminals of the stator relative to the second end shield sothat they can easily be connected with female electric connectors of anelectronics package associated with the motor as it is connected to thesecond end shield.

Both the first and second end shields are formed with generally squareperipheral configurations and with four columns projectinglongitudinally from the four corners of their square configurations.Each of the four columns of the end shields is formed with a flat basesurface that mates against one of the first and second end surfaces ofthe stator stack. In addition, adjacent the base surfaces of thecolumns, shoulders project longitudinally outwardly from the basesurfaces. The shoulders are formed with shoulder surfaces that overliethe pairs of flat surfaces on the exterior surface of the stator stack.The engagement of the column shoulder surfaces over the flat surfaces onthe exterior of the stator stack securely holds the first and second endshields to the opposite first and second end surfaces of the statorstack preventing relative torsional or radial movement between the endshields and the stator stack.

With the design of the component parts of the electric motor describedabove, the size of the motor can be significantly reduced while avoidingthe potential problems of securely connecting component parts of themotor together and insulating, both electrically and thermally, theelectrical component parts of the motor from structural component parts.

DESCRIPTION OF THE DRAWINGS

Further features of the invention will be discussed in the followingdetailed description of the preferred embodiment of the invention and inthe drawing figures wherein:

FIG. 1 is an exploded perspective view of the electromagnetic device ofthe invention;

FIG. 2 is a plan view of a stator lamination of the device;

FIG. 3 is a perspective view of the stator stack;

FIGS. 4A-4C are back, side sectional and front views of the first endcap;

FIGS. 5A-5C are front, side sectional and rear views of the second endcap;

FIGS. 6A-6C are front perspective, rear perspective and side sectionalviews of the insulator;

FIGS. 7A-7C are front perspective, rear perspective and side sectionalviews of the second end shield;

FIGS. 8A-8C are front perspective, rear perspective and side sectionalviews of the first end shield;

FIG. 9 is a side sectional view of the electromagnetic device assemblywith the rotor positioned in the stator, the end caps assembled toopposite ends of the stator, and the first end shield containing abearing assembled to the first end of the stator;

FIG. 10 is a side sectional view similar to FIG. 9 but with the additionof the insulator assembled to the stator;

FIG. 11 is similar view to FIG. 10 but with the addition of the secondend shield assembled to the stator;

FIG. 12 is a view similar to FIG. 11 but with an electronics packageassembled to the second end shield;

FIG. 13 is a side elevation view of the completed electromagneticdevice; and

FIG. 14 is a first end view of the electromagnetic device shown in FIG.13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 shows the primary component parts that make up theelectromagnetic device 18 of the invention including the stator stack20, a first end cap 22, a second end cap 24, an insulator 26, a firstend shield 28, a second end shield 30 and a rotor 32. In FIG. 1 anelectronics package 34 is also shown adjacent the second end shield 30.The particular electronics package 34 shown is an encoder, however othertypes of electrical devices commonly employed with electromagneticdevices such as motors or generators may be substituted for the encodershown as the electronics package 34. The electronics package 34 isincluded in the description of the invention to illustrate the ease withwhich such an electronics package may be connected with the electricalleads of the electromagnetic device 18 due to the novel constructions ofcomponent parts of the device. It should be understood that theparticular electronics package 34 shown is not intended to be construedas one of the novel features of the electromagnetic device constructionand that other types of devices may or may not be employed with theelectromagnetic device of the invention.

The stator 20 is constructed of a plurality of stator laminations 36such as that shown in FIG. 2, which is typical of many statorconstructions. Each of the laminations 36 has a generally octagonalperipheral edge 38 and a plurality of stator poles 40 that projectradially inwardly toward a center bore 42 of the laminate, again as istypical in many constructions. Each of the stator poles 40 is stampedwith an indent/protrusions 44 with an indentation on one side of eachpole and a protrusion on the opposite side of each pole. The protrusionsand indents of adjacent laminates in the stator stack engage with eachother to hold the laminates of the stator stack together. Adjacent theperipheral edge 38, each laminate has a plurality of holes 46 extendingtherethrough. The holes 46 may be used in aligning the laminates whenassembling the stator stack, but are primarily provided to receiveprojecting tabs on the second end cap when attaching the second end capto the stator stack, as will be described. Grooves 48 are also formed inthe peripheral edge 38 of the laminates. These grooves 48 are positionedto receive tabs on the first end cap when attaching the end cap to thestator stack as will be described.

The octagonal shape of the peripheral edge 38 is partly defined by fourpairs of flats 50 formed in the peripheral edge at spatially arrangedpositions. Each pair of flats 50 has a semi-circular trough 52positioned therebetween. When the laminates 36 are arranged in the stack20 as shown in FIG. 3, the pairs of flats 50 and their troughs 52 formpairs of flat surfaces 54 that extend along the entire longitudinallength of the stator stack 20 between a first end surface 56 of thestator stack and a longitudinally opposite second end surface 58 of thestator stack. Each of the pairs of flat surfaces 54 on the exterior ofthe stator stack border a semi-circular trough 60 that also extends theentire longitudinal length of the stator stack between the opposite endsurfaces 56, 58. The pairs of flat surfaces 54 on the stator exteriorsurface are provided to positively locate the end shields 28, 30relative to the stator and to prevent torsional and/or radial movementof the end shields relative to the stator stack as will be explained.The trough surfaces 60 formed in the stator stack are provided toaccommodate bolt fasteners as also will be explained.

FIGS. 4A-4C show the first end cap 22. The first end cap 22 ispreferably constructed of an electrically insulating material such as aplastic. The end cap has opposite rear 66 and front 68 surfaces with therear surface being that which faces the stator stack 20 and the frontsurface being that which faces away from the stator stack. The end capalso has a peripheral edge 70 that is generally square except for fourcurved notches 72 in place of the corners of the end cap squareconfiguration. The end cap also includes a plurality of posts 74 thatradiate inwardly toward a center bore 76 of the end cap. The posts 74are configured complimentary to the stator poles 40 and overlay thestator poles when the cap is assembled to the first end surface 56 ofthe stator stack. The end turns of the stator winding are wrapped aroundeach of the end cap posts 74 and the posts insulate the end turns fromthe metal of the stator poles 40. The first end cap has four tabs 78projecting outwardly from its rear surfaces 66. The four tabs 78 arespatially arranged around the peripheral edge 70 of the end cap to alignwith and be received in the grooves 48 of the stator stack when thefirst end cap is assembled to the first end surface 56 of the statorstack.

A spacer 80 projects longitudinally outwardly from the front surface 68of the first end cap The spacer 80 is preferably cylindrical andsurrounds all of the posts 74 of the first end cap. The spacer 80 isdimensioned sufficiently large so that it will project longitudinallyfrom the end cap front surface 68 a distance beyond the end turns of thestator windings around the end cap posts 74. When the first end shield28 is assembled to the stator stack 20 over the first end cap 22, thespacer 80 will engage with an interior surface of the first end shield28 and will thereby space the metal end shield from the end turns of thestator windings preventing any shorting of the end turns with the metalof the end shield. In the preferred embodiment the spacer 80 has thecylindrical configuration shown. However, the spacer could beconstructed as one or more posts extending longitudinally from the firstend cap to the same longitudinal extent as the spacer 80 shown. However,the cylindrical configuration of the spacer 80 is preferred for itsstrength.

The second end cap 24 is shown in FIGS. 5A-5C. Like the first end cap,the second end cap is also constructed of an electrically insulatingmaterial such as a plastic. The second end cap has a rear surface 86 andan opposite front surface 88, with the rear surface 86 being that whichfaces the stator stack 20 and the front surface 88 being that whichfaces away from the stator stack. The second end cap also has agenerally square peripheral edge 90 except for four notches 92 in placeof the corners of the generally square configuration. The second end capalso includes a plurality of posts 94 around a center bore 96 of the endcap. The posts 94 are substantially identical to the posts 74 of thefirst end cap and are provided for the same functioning. Four tabs 98project outwardly from the rear surface 86 of the end cap and arepositioned to align with four of the holes 46 in the second end surface58 of the stator stack in attaching the second end cap 24 to thissurface of the stator stack.

In addition, the second end cap is provided with supports 100 for maleterminal connectors that are connected to electrical leads of the statorwinding. The supports 100 have center passages (not shown) that extendthrough the supports 100. The supports 100 positively position the maleelectric terminals of the stator winding to facilitate the assembly ofthe component parts of the electromagnetic device and the connection ofthe terminals to the female terminal connectors of the electronicspackage, as will be explained.

The insulator 26 is shown in FIGS. 6A-6C. Preferably, the insulator 26is constructed of a material that is both electrically and thermallyinsulating. The insulator is constructed with an interior surface 106and an exterior surface 108, the interior surface 106 surround thesecond end cap 24 when the insulator is assembled to the electromagneticdevice. A peripheral edge 110 of the insulator has a generally squareconfiguration except for notches 111 in place of the corners of thesquare configuration. The insulator peripheral edge 110 is complimentaryto the peripheral edge 90 of the second end cap and extends completelyaround the edge of the second end cap when the insulator is assembledover the end cap. The sides of the insulator 113 closest to the secondend cap 24 actually surround the stator winding turns on the second endcap. This particular construction of the insulator enables an overallreduction in the width of the motor. By employing these portions of theinsulator sides 113 to surround the stator winding turns on the secondend cap 24, the sides of the insulator, being constructed of anelectrically insulating material, can be positioned much closer to thestator end turns than could an end shield constructed of metal. An endshield constructed of metal would have to be constructed with a greaterwidth in order to ensure the metal of the end shield sides is spacedfrom the end turns of the stator to avoid contact and shorting of themetal end shield sides with the stator turns. By replacing the prior artend shield construction with the insulator 26 having sides 113 thatsurround the stator turns, the overall lateral width of the motor isreduced. A center hole 112 of the insulator is dimensioned sufficientlylarge to enable a bearing mounting collar of the second end shield 30 toextend therethrough, but still enables the insulator to providesufficient coverage of the end turns of the stator over the second endcap posts 94 to insulate the windings from the metal of the second endcap 24. In addition, the insulator thermally insulates any electroniccomponents used in association with the motor and attached to the secondend shield from the heat generated in the stator.

The insulator also has a plurality of tubular lead guides 114 projectinglongitudinally from the exterior surface 108 of the insulator. Thenumber of lead guides 114 and their positioning on the insulatorcorresponds to the number and positioning of the male terminal supports100 on the second end cap 24. With the insulator 26 assembled over thesecond end cap 24, the terminal supports 100 of the second end cap andthe male terminals of the stator electrical leads they support projectthrough the interiors of the lead guides 114. Thus, the tubular leadguides 114 with the electrical lead supports 100 positively position themale terminals of the stator where they can be easily connected withmating female electrical connectors of a separate electronics package 34used in association with the electromagnetic device as the package isassembled to the second end shield 30. As the electronics package isconnected to the second end shield 30, the female connectors arepositioned on the electronics so that they will extend into the tubularlead guides 114 of the insulator. The tubular lead guides 114 functionto guide the male terminals of the stator into the mating femaleterminals of the electronics package as the package is assembled to thesecond end shield 30. This enables a blind assembly of the electronicspackage onto the second end shield. With the insulator lead guides 114guiding the female connectors over the male terminals, a good connectionis ensured. In addition, the tubular lead guides 114 insulate theelectric terminals from contact with the metal of the second end shield30 as they extend through the end shield to its exterior surface wherethey can be connected to a separate electronics package.

The second end shield 30 is shown in FIGS. 7A-7C. In the preferredembodiment the second end shield 30 is constructed of metal, as isconventional. The second end shield 30 has a generally squareconfiguration with opposite interior 120 and exterior 122 surfaces. Theinterior surface 120 is that which faces toward the stator stack 20. Ashaft opening 124 passes through the end shield and is surrounded by acircular collar 126 that extends axially from the end shield interiorsurface 120. The collar 126 is provided to hold a bearing assembly thatin turn mounts the rotor 32 for rotation on the end shield, as istypical in electric motor construction.

The peripheral edge of the end shield includes four columns 128 thatproject longitudinally and axially outwardly from the end shieldinterior surface 120. It can best be seen in FIG. 7B that the peripheralside wall 129 of the second end shield does not extend the full lengthof the columns 128 leaving spaces between the columns 128 adjacent theirdistal ends. These spaces are provided to accommodate the side walls 113of the insulator. The columns 128 reach beyond the insulator side walls113 when attaching the second end shield to the stator. By eliminatingthe sections of the metal side walls from the second end shield andreplacing them with portions of the insulator side walls 113 thatsurround the stator end turns on the second end cap 24, the width of thesecond end shield and the overall width of the motor can be reducedwhile avoiding positioning the metal side walls of the second end shieldtoo close to the stator end turns where the possibility of electricalshorting would exist. Each of the columns 128 has a fastener hole 130extending therethrough. In addition, each of the columns has a basesurface 132 formed thereon. As seen in FIG. 7B, the base surface 132 ofeach column 128 intersects the fastener hole 130. Shoulders 134 extendlongitudinally outwardly from the base surfaces 132 of the columns todistal end surfaces 136 of each of the columns. Shoulder surfaces 138extend between the base surfaces 132 and the end surfaces 136 of thecolumns. In the preferred embodiment of the invention, the base surfaces132 are coplanar and are formed to mate complimentary with the secondend surface 58 of the stator stack. In addition, the shoulder surfaces138 are positioned to overlay and engage against pairs of flat surfaces54 on the exterior surface of the stator stack with the fastener hole130 of each column aligning with a trough 60 between the stator flatsurfaces 54. The mating engagement of the shoulder surfaces 138 with theflat surfaces 54 of the stator stack secures the second end shield 30against radial and/or torsional movement relative to the stator stack.In this manner, nut and bolt fasteners passing through the fastenerholes 130 of the second end shield 30 and the troughs 60 across theexterior surface of the stator stack 20, in addition to the engagementof the shoulder surfaces 138 with the flat surfaces 54 on the exteriorof the stator stack, securely hold the second end shield 30 stationaryrelative to the stator stack 20. By combining the engagement of theshoulder surfaces 138 against the stator flat surfaces 54 with a nut andbolt fastener to hold the second end shield to the stator stack 20, amuch stronger connection is provided than by using a fastener alone. Inaddition, a smaller nut and bolt fastener may be used therebycontributing to the reduction in size of the overall electromagneticdevice 18.

The second end shield 30 also has a number of lead openings 140 passingtherethrough. The lead openings 140 have configurations and positions onthe second end shield 30 that corresponds to the tubular lead guides 114of the insulator 26. When the second end shield 30 is assembled to thestator stack 20 over the insulator 26, the tubular lead guides 114extend through the lead openings 140 of the second end shield andthereby insulate the electrical leads of the stator from contacting themetal of the second end shield 30.

The peripheral edge 142 of the second end shield 30 is also providedwith a pair of diagonally opposed holes 144 and a pair of diagonallyopposed posts 146. The holes 144 and posts 146 provide a simple methodof connecting an external electronics packages 34 to the second endshield 30.

The first end shield 28 is similar to the second end shield 30 andtherefore will not be described in the same detail. In the preferredembodiment, the first end shield 28 is constructed of metal and also hasa generally square configuration defined by its peripheral edge 152. Theend shield has opposite interior 154 and exterior 156 surfaces with ashaft opening 158 passing therethrough. The first end shield also hasfour columns 160 projecting axially and longitudinally from the interiorsurface 154. Like the columns of the second end shield, the four columns160 include base surfaces 162 and shoulders 164 with the shouldershaving shoulder surfaces 166 and distal end surfaces 168 of the columns.A fastener hole 170 extends through each of the columns 160 and isintersected by the base surfaces 162.

The shoulder surfaces 166 and base surfaces 162 of the first end shieldcolumns 160 function in the same manner as those of the second endshield columns 128. In addition, the fastener holes 170 of the first endshield columns 160 align with the troughs 60 on the exterior surface ofthe stator stack 20 in the same manner as the fastener holes 130 of thesecond end shield columns. The shoulder surfaces 166 and the flats 54 ofthe stator stack mate with each other to securely hole the first endshield 28 against torsional and/or radial movement relative to thestator stack in the same manner as the second end shield 30.

FIGS. 1 and 9-14 illustrate the assembly of the component parts of theelectromagnetic device 18 of the invention. In FIG. 9, the first end cap22 and second end cap 24 have been attached to the longitudinallyopposite first end surface 56 and second end surface 58 of the statorstack 20. The first end shield 28 is attached to the stator stack 20over the first end cap 22. The shaft of the rotor 32 is shown supportedin a bearing 180 supported by the first end shield 28 in a conventionalmanner. The stator winding has been added to the stator stack 20 and theend turns are schematically represented at the first end 176 and secondend 178 of the stator stack. It can be seen in FIG. 9 that the spacer 80surrounds the end turns 176 of the stator winding and projectslongitudinally beyond the end turns 176 to space the first end shield 28from the end turns 176 and thereby prevent any shorting of the statorwinding with the first end shield. At the second end surface 58 of thestator stack the electrical lead supports 100 of the second end cap 24support stator leads 182.

FIG. 10 shows the insulator 26 assembled over the second end cap 24. Theinsulator peripheral edge 110 extends completely around the second endcap 24 and one of the insulator tubular lead guides 114 is shownsurrounding the stator electrical lead 182 supported by the second endcap lead support 100.

FIG. 11 shows the second end shield 30, with a bearing 184 inserted intoits bearing collar 126, assembled over the insulator 26. The bearing 184supports the shaft of the rotor 32 in a conventional manner. Theinsulator lead guides 114 surrounding the stator electrical leads 182project through the lead openings 140 of the second end shield 30 andproject a short distance outwardly from the end shield exterior surface122 where they can be easily accessed for connection with an externalelectronics package. The insulator 26 also spaces the second end shield30 from the end turns 178 of the stator winding and electricallyinsulates the end turns 178 from the end shield 30. The insulator 26also provides thermal insulation and for electronics attached to theexterior surface 122 of the end shield 30.

Referring to FIG. 1, a plurality of bolts 186 are inserted through thefastener holes 130 of the second end shield 30 and pass through thenotches 111 of the insulator 26 and the notches 90 of the second end cap24 and through the trough surface 60 on the exterior of the stator stack20. The bolts 186 then pass through the notches 72 in the periphery ofthe first end cap 22 and through the fastener holes 170 of the first endshield 28. The ends of the bolts 186 can be screw threaded intocomplimentary internal threading in the fastener holes 170 of the firstend shield 28 or can be threaded into nuts on the exterior surface 156of the first end shield 128. The bolts 186, together with the shouldersurfaces of the end shields described earlier, securely hold togetherthe component parts of the electromagnetic device 18.

FIGS. 1 and 12-14 also show an external electronics package 34 assembledto the second end shield 30 of the electromagnetic device. As shown inFIG. 1, the electronics package 34 includes a printed circuit board withelectronics modules attached (PC board) 192 having holes 194 at each ofits corners. The PC board holes 194 correspond to the peripheral edgeholes 144 and peripheral edge posts 146 of the second end shield 30. Asquare housing wall 96 that could be constructed of metal or othermaterial that would enable it to function as a heat sink as well as anenclosure for the PC board 192 is positioned over the PC board. Thehousing wall 196 has diagonally opposed grooves 198 at opposite interiorcorners. A housing cover 200 fits against the wall 196 and a pair ofbolts 202 pass through holes 204 in the cover, through the housing wallgrooves 198, through the PC board holes 194 and into the peripheral edgeholes 144 of the second end shield 30. Internal threading in theperipheral edge holes 144 of the second end shield 30 securely attachesthe electronics package 34 to the second end shield. The electronicspackage 34 can be constructed so that any electrical connectors of thepackage will coincide in position with the electrical leads 182 of theelectromagnetic device 18 so that attaching the electronics package 34to the second end shield 30 of the device also completes the electricalconnections between the electronics package and the device.

From the above description it can be seen that by the design of thecomponent parts of the electromagnetic device 18, the size of the deviceis significantly reduced while avoiding the potential problems ofsecurely connecting the component parts of the device together andinsulating, both electrically and thermally, the electrical componentparts of the device from structural component parts.

While the present invention has been described by reference to aspecific embodiment, it should be understood that modifications andvariations of the invention may be constructed without departing fromthe scope of the invention defined in the following claims.

What is claimed:
 1. An electromagnetic device comprising: a stator stackhaving a longitudinal length with longitudinally opposite first andsecond end surfaces, an exterior surface between the first and secondend surfaces and a center bore through the stator stack between thefirst and second end surfaces, first and second end shields coveringover the respective first and second end surfaces of the stator stack,the first and second end shields each have a shaft opening aligned withthe center bore of the stator stack, each of the end shields has a basesurface that mates against one of the first and second end surfaces ofthe stator stack, and the first end shield has a shoulder that projectsoutwardly from the base surface of the first end shield and overlays aportion of the stator stack exterior surface, the shoulder has ashoulder surface that mates against the portion of the stator stackexterior surface and resists a relative torsional movement between thestator stack and the first end shield, the base surface and the shouldersurface are perpendicular to each other, the shoulder surface and theportion of the stator stack exterior surface are both flat surfaces;and, a plurality of threaded fasteners extend between the first andsecond end shields through the base surfaces of the first and second endshields and over the exterior surface of the stator stack and secure thefirst and second end shields to the respective first and second endsurfaces of the stator stack.
 2. The electromagnetic device of claim 1,wherein: the first end shield has a pair of base surfaces that mateagainst the first end surface of the stator stack and a pair ofshoulders that project outwardly from the pair of base surfaces andoverlay portions of the stator stack exterior surface on laterallyopposite sides of the stator stack.
 3. The electromagnetic device ofclaim 2, wherein: the pair of shoulders have shoulder surfaces that mateagainst the portions of the stator stack exterior surface on laterallyopposite sides of the stator stack and the shoulder surfaces and theportions of the stator stack exterior surface are all flat.
 4. Theelectromagnetic device of claim 1, wherein: the stator stack center borehas a center axis and the shoulder surface and the portion of the statorstack exterior surface are parallel with the center bore center axis. 5.The electromagnetic device of claim 1, wherein: the second end shieldhas a shoulder that projects outwardly from the base surface of thesecond end shield and overlays a second portion of the stator stackexterior surface, the second end shield shoulder has a shoulder surfacethat mates against the second portion of the stator stack exteriorsurface and resists a relative torsional movement between the statorstack and the second end shield.
 6. The electromagnetic device of claim5, wherein: the portion of the stator stack exterior surface that theshoulder of the first end shield overlays and the second portion of thestator stack exterior surface that the shoulder of the second end shieldoverlays are portions of one flat surface that extends longitudinallyacross the exterior surface of the stator stack between the first andsecond end surfaces of the stator stack.
 7. The electromagnetic deviceof claim 6, wherein: at least one fastener of the plurality of fastenersoverlays the portion of the stator stack exterior surface that theshoulder of the first end shield overlays and the second portion of thestator stack exterior surface that the shoulder of the second end shieldoverlays.
 8. The electromagnetic device of claim 5, wherein: the secondend shield has a pair of base surfaces that mate against the second endsurface of the stator stack and a pair of shoulders that projectoutwardly from the pair of base surfaces and overlay portions of thestator stack exterior surface on laterally opposite sides of the statorstack.
 9. The electromagnetic device of claim 8, wherein: the pair ofshoulders of the second end shield have shoulder surfaces that mateagainst portions of the stator stack exterior surface on laterallyopposite sides of the stator stack and the shoulder surfaces and theportions of the stator stack exterior surface are all flat.
 10. Anelectromagnetic device comprising: a stator stack having a longitudinallength with longitudinally opposite first and second end surfaces, anexterior surface between the first and second end surfaces, a centerbore through the stator stack between the first and second end surfaces,and a stator winding around the center bore; an end cap covering overthe first end surface of the stator stack; a first end shield coveringover the end cap, the end cap spacing the first end shield from thestator winding; an insulator covering over the second end surface of thestator stack; a second end shield covering over the insulator, theinsulator insulating the stator winding from the second end shield; and,the insulator has a tubular lead guide that projects longitudinally fromthe insulator, the stator winding has an electric terminal that issupported in the insulator tubular lead guide, the second end shield hasa lead opening and the insulator tubular lead guide passes through thelead opening.
 11. The electromagnetic device of claim 10, wherein: theend cap has a spacer that projects longitudinally from the end cap andengages with the first end shield and thereby maintains a spacingbetween the first end shield and the stator windings.
 12. Theelectromagnetic device of claim 10, wherein: the tubular lead guide hasa distal end with an opening therein providing access to the electricterminal supported by the lead guide through the opening, the openingbeing adapted to guide a separate electric terminal inserted through theopening onto the terminal supported in the lead guide.
 13. Anelectromagnetic device comprising: a stator stack having a longitudinallength with longitudinally opposite first and second end surfaces, anexterior surface between the first and second end surfaces, a centerbore through the stator stack between the first and second end surfaces,and a stator winding around the center bore; an end cap covering overthe first end surface of the stator stack; a first end shield coveringover the end cap, the end cap spacing the first end shield from thestator winding; an insulator covering over the second end surface of thestator stack; a second end shield covering over the insulator, theinsulator insulating the stator winding from the second end shield; and,the first end shield has longitudinally projecting columns that extendpast the end cap and engage with the first end surface of the statorstack.
 14. The electromagnetic device of claim 13, wherein: the secondend shield has longitudinally projecting columns that extend past theinsulator and engage with the second end surface of the stator stack.15. The electromagnetic device of claim 14, wherein: the first endshield and the second end shield each have four of said columns.
 16. Theelectromagnetic device of claim 14, wherein: the columns of the firstend shield each have a shoulder surface that mates against a portion ofthe stator stack exterior surface and resists a relative torsionalmovement between the stator stack and the first end shield and thecolumns of the second end shield each have a shoulder surface that matesagainst a portion of the stator stack exterior surface and resists arelative torsional movement between the stator stack and the second endshield.
 17. The electromagnetic device of claim 16, wherein: theshoulder surfaces of the columns of the first and second end shields andthe portions of the stator stack exterior surface are all flat surfaces.18. An electromagnetic device comprising: a stator stack having alongitudinal length with longitudinally opposite first and second endsurfaces, an exterior surface between the first and second end surfaces,a center bore through the stator stack between the first and second endsurfaces, and a stator winding around the center bore; an end capcovering over the first end surface of the stator stack; a first endshield covering over the end cap, the end cap spacing the first endshield from the stator winding; an insulator covering over the secondend surface of the stator stack; a second end shield covering over theinsulator, the insulator insulating the stator winding from the secondend shield; and, an external electronics package is connected to thesecond end shield on an opposite side of the second end shield from theinsulator and the insulator provides both thermal and electricalinsulation of the stator winding from the external electronics package.